--- a/ChangeLog
+++ b/ChangeLog
@@ -1,3 +1,14 @@
+2013-01-20  Bernhard Voelker  <mail@bernhard-voelker.de>
+
+	bootstrap: remove the need for a sorted .gitignore file
+	* build-aux/bootstrap (insert_sorted_if_absent): Adjust and
+	rename to insert_if_absent(), so that we don't need or generate
+	a sorted .gitignore file.  We do require a .gitignore with no
+	existing duplicate entries and enforce that.
+	(sort_patterns): Remove this function as we now use the simpler
+	technigue of inserting blacklist entries at the top of the file,
+	assuming gnulib won't be inserting !whitelist entries.
+
 2013-01-23  Paul Eggert  <eggert@cs.ucla.edu>
 
 	readlinkat: don't depend on gl_FUNC_OPENAT

--- a/build-aux/bootstrap
+++ b/build-aux/bootstrap
@@ -1,6 +1,6 @@
 #! /bin/sh
 # Print a version string.
-scriptversion=2012-12-28.10; # UTC
+scriptversion=2013-01-20.16; # UTC
 
 # Bootstrap this package from checked-out sources.
 
@@ -306,34 +306,34 @@
   die "Bootstrapping from a non-checked-out distribution is risky."
 fi
 
-# Ensure that lines starting with ! sort last, per gitignore conventions
-# for whitelisting exceptions after a more generic blacklist pattern.
-sort_patterns() {
-  sort -u "$@" | sed '/^!/ {
-    H
-    d
-  }
-  $ {
-    P
-    x
-    s/^\n//
-  }' | sed '/^$/d'
+# Strip blank and comment lines to leave significant entries.
+gitignore_entries() {
+  sed '/^#/d; /^$/d' "$@"
 }
 
-# If $STR is not already on a line by itself in $FILE, insert it,
-# sorting the new contents of the file and replacing $FILE with the result.
-insert_sorted_if_absent() {
+# If $STR is not already on a line by itself in $FILE, insert it at the start.
+# Entries are inserted at the start of the ignore list to ensure existing
+# entries starting with ! are not overridden.  Such entries support
+# whitelisting exceptions after a more generic blacklist pattern.
+insert_if_absent() {
   file=$1
   str=$2
   test -f $file || touch $file
-  echo "$str" | sort_patterns - $file | cmp -s - $file > /dev/null \
-    || { echo "$str" | sort_patterns - $file > $file.bak \
-      && mv $file.bak $file; } \
-    || die "insert_sorted_if_absent $file $str: failed"
+  test -r $file || die "Error: failed to read ignore file: $file"
+  duplicate_entries=$(gitignore_entries $file | sort | uniq -d)
+  if [ "$duplicate_entries" ] ; then
+    die "Error: Duplicate entries in $file: " $duplicate_entries
+  fi
+  linesold=$(gitignore_entries $file | wc -l)
+  linesnew=$(echo "$str" | gitignore_entries - $file | sort -u | wc -l)
+  if [ $linesold != $linesnew ] ; then
+    { echo "$str" | cat - $file > $file.bak && mv $file.bak $file; } \
+      || die "insert_if_absent $file $str: failed"
+  fi
 }
 
 # Adjust $PATTERN for $VC_IGNORE_FILE and insert it with
-# insert_sorted_if_absent.
+# insert_if_absent.
 insert_vc_ignore() {
   vc_ignore_file="$1"
   pattern="$2"
@@ -344,7 +344,7 @@
     # .gitignore entry.
     pattern=$(echo "$pattern" | sed s,^,/,);;
   esac
-  insert_sorted_if_absent "$vc_ignore_file" "$pattern"
+  insert_if_absent "$vc_ignore_file" "$pattern"
 }
 
 # Die if there is no AC_CONFIG_AUX_DIR($build_aux) line in configure.ac.